This invention relates to a combustor, and more particularly to an integrated polymeric-ceramic membrane-based oxy-fuel combustor.
Carbon capture is essential to continue the use of fossil fuels while reducing the emissions of CO2 into the atmosphere. Oxy-fuel combustion is an emerging methodology for carbon capture in power and steam generation systems. In oxy-fuel combustion, the fuel is burned in a nitrogen-free environment (pure oxygen diluted with CO2 and H2O) instead of air. Thus, the flue gas mainly consists of CO2 and H2O that can be easily separated through condensation of H2O. In order to moderate the gas temperature in the absence of N2, part of the flue gases including CO2 is recycled back to the combustion chamber. Among different methods for O2 production, membrane separation is well suited for small-scale and oxygen-enriched air requirements [1, 2]. Membrane separation material options generally fall into one of two categories, polymeric or ceramic. These two membrane types provide very different performance and operating characteristics. The first, polymer membranes, operate at ambient temperatures. Polymer membranes [3] are usually considered for producing O2-enriched air. Polymer membranes and/or zeolites are good for oxygen separation. However, the purity of oxygen is not high, in particular not sufficiently high for oxyfuel combustion with efficient carbon capture. The second type is the high-temperature ceramic membrane or Ion Transport Membranes (ITM). Ceramic membranes produce very high purity oxygen, but they require high operating temperatures [4] and have higher material cost per productivity [5]. The permeability (oxygen flux rate) of ITMs depends on the partial pressure of O2 in the oxygen-nitrogen mixture. Increasing the concentration of O2 by using O2-enriched air rather than air improves the performance of the ITM. Combining polymeric with ceramic membranes can, thus, improve the overall efficiency of the system.